Arc-lamp electrode.



we /a site-comm.- COATING R ms'nc 4 UNITED STATES PATENT OFFICE.

EXAMINER W BOY MOTT, 01: LAKEWOOD, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS,TO I NATIONAL CARBON OOMPANY,.INO., A CORPORATION OF NEW YORK.

ans-am nnnc'rnons.

To all whom it may concern:

Be it known that I, WILLIAM R. Mo'rr,

a citizen of the United States, and resident of Lakewood, in thecounty.of Cuyahoga 5 and State of Ohio, have invented a certam newanduseful Im rovement in Arc-Lam Electrodes, of whic the following is ain clear, and exact description.

This invention relates to are lam electrodes containing rare-earth metaluorids and more particular y a me o o rea ing arare-earth metal fluoridcontaining a cesrgin per of combined sulfur trioxii as asu ate impurityw ere y t e Frau 1%:

g material is made advantageous for use in arc lamp electrodes. Theserare-earth metal fluorids are obtained from the residue of ds after theremova o e t onuifwliich 1s used in the well known Welsbach mantles.,Usually the material known as Welsbach residue .consists of thesulfates of cerium with other rare-ea!" me a sn :1 es

...- M 1111mm,

' mlxe such as lanthanum, neoc raes'eod um and ttmum and somelmpurities. T ese lf convert th su ates into fluorids they at hWma-mfi pcipitate the insolu e rare-earth metal fluorids. The product 0 1sprecipitation so contains more or less sulfates which cannot be readilywashed out. While the manner in which the sulfur trioxid (S0,) iscombined is not certain, it is robable that it is combined in the form 0rare-earth metal 85 sulfates or basic sulfates. v

ough e a ove escribed process for making rare-earth fluorids is the onecommonly used, it should be understood that this invention is notlimited to the use of 40 rare-earth fluorid made by above process,

but is ap licable to rare-earth fluorid contamina with sulfate made byany process whatsoever.

The use of rare-earth metal fluorids con-.

taining rare-earth 'metal sulfates in an arc lam electrode has severaldisadvantages.

In e first place, the fluorin content is decreased, which increases thetendency tov form insulating beads. of slag on the ends 60 of thecarbons. Further, the hy oscopic nature of the rare-earth metal. ates m-Specification of Letters Patent.

Patented Oct. 23, 1917.

Application filed November 6, 1916. Serial No. 129 677.

' terferes with'the normal baking of solid or homogeneous flame carbonsand tends to cause an'undue increase in hardness of carbons, whlch initself increases the slagging tendency. When heated to moderatetemperatures, alone or in flame carbons in the absence of salts forminginsoluble sulfates, rare-earth metal sulfates liberate some sulfurtrioxid (S0,) which combines with any water vapor to form sulfuric acidand this tends to produce corrosion of the metal parts of the lam s. Thereaction of free sulfur trioxid 0,) in the presence of water vapor withrare-earth metal fluorids also liberates hydrofluoric acid whichincreases the globe etching. A ain, the presence of-rare-earth metal sulates also has been found to decrease the candle power. Since therare-earth sulfates are-somewhat soluble and hygroscopic, they causecoagulation of the silicate bmder in cored carbons thus reducmg e timatestrength an compactness of the core and even permitting portions of thecore to fall out.

According to the present invention these dlsadvantages of the rare-earthsulfates are eliminated by adding certain insoluble swater insoluble)fiuog'ds to the materials con mmg e rare-cart metal spl fates tofacilitate the form insoluble sulfates and rare-earth fluoridstherefrom. The in soluble fluorids suitable for this purpose must alsoform sulfates, insoluble in water, such as fluorids of barium, strontiumand lead, although I Have found Banum fluorid W most satisfactory.

When rare-earth metal sulfate is heated with barium fluorid, thefollowing reaction occurs:

the barium fluorid may be added before [4o bin the usual calcination andthe two results accomplished by the same heating. The calcining. may becarried out by heating to I ,from 500 This method can be advanagetasrytss with fluorids intended for cored flame carbons althoughthere is no disadvantage in the case of solid flame carbons. However,since solid flame carbons are baked to set the itch binder the bariumfluorid need not be added until after baking of the electrodeswill bringabout the desired reaction between the bariumv fluorid'and thesulfate'montent, which b i; iransposition gives the insoluble stable suI ate...

heat of the arc may berelied upon to bring Also. under certainconditions the about-the reaction; i

Both the barium sulfate and the rare-earth 2 fluorids resulting from thereaction are insoluble in water and practically non-hygroscopic.Therefore the silicate binder of the coring material for core ame carwill not be coagulated. 'When used in solid flame carbons,-these saltsdo not tend to produce hard carbons of such a textureand nature as toincrease slagging. The resulting barium sulfate is also a desirablematerial because it possesses 00d 0 flaming properties and increases theli eof the electrodes. 1

Most are lamp electrodes containing flam ing materials have calciumfluorid as a con stituent and'when impure rare-earth fluorids arecombined therewith in the electrode, cal-' cium sulfate is formedto someextent by reacting on the sulfate content. In cored carbons calciumsulfate is suflicientl soluble to cause coagulation of the alkahsilicate which gives an inferior carbon. In e co r6 es having both thefluorids of barium and calcium, barium sulfate will be formed morereadil Be v cial effect is obtained if from one-halfto. five per cent.of barium fluorid is added for each per 'cent. of sulfur trioxid (S0,) ain the rare-earth fluorids. As a rule, a slight Lexcess of bariumfluorid above that calfrom the equation is tobe preferred.

'of the combination of rar eart m H'avmg dscfiBeEI my mventiom'what Iclaim is:

' fate.

than calcium because of its' greater stability and the greater heatliber-y seated in its formation. r

' As a flame mix for solid flame carbons, the following is given by theway of are ample:

Rare-earth metal fluorids. which may contain two to three per 7G I cent.of SO, as sulfate impurity About-4Q parts of the above mix 1s co'm-'bined with 60 partsofa carbon flour base andforced with suitable binderand baked in a,man'ne rfwell known, to makers of flame carbons.

While my invention described chiefly 8Q in'con'nection with thetreatment if im ure lu': i u ,itisnotnecessar ited thei'etol "fotheraspect of the invention is the treatment 'of rare-earthmetal 3'5 sulfatewith barium fluoridto form rareearth fluorid. Still another aspect .ofthe invention is the use in arc lam electrodesmetal sul;

fates and barium fluori uorids an arium an a e 1. The process of makingan arc lamp electrode which consists in mixing rare- 9 earth metalfluorids containing sulfates with an insoluble fluorid of an elementforming an insoluble sulfate.

2.-The process of making an arc lamp veelctrode which consists in mixing'rareearth metal fluorids containing sulfates with an insoluble fluoridof an element forming an insoluble sulfate and heating to formrare-earth metal fluorid and an insoluble sul- 3. The process of makingrare-earth meta fluorids which consists in adding barium fluorid torare-earth metal sulfates and cal cining h.

v 4. e process of eliminating sulfates me from rare-earth metal fluoridswhich con sists in adding barium fluorid thereto and. calcining.

5. The process of eliminating rare-earth metal sulfates from rare-earthmetal fluorids which consists in adding barium fluorid thereto andcalcinin to form barium sulfate and rare-earth uorids. I

6. The process of maln'ng an arc lamp' electrode which consists inmixing rareearth metal fluorids containing sulfates with barium fluorid.

7. The process of making an arc lamp electrode which consists in mixingrare earth metal fluorids containin rare-earth metal sulfates withbarium fluorid and heating to form rare-earth metal fluorids and bariumsulfate. y

8. The process of making an arc lamp electrode which consists in mixinga. binder, lac

carbon and rare-earth metal fluoride containing rare-earth. metalsulfates with barium fluorid and baking to set the binder and formrare-earth metal fluoride and metal'fluorids contaming a small amountofsulfate and barium fluorid mounting to from one-half to fivetimes theweight of EXAMINER combined sulfur trioxid (S0,) contained in thesulfate of the rare-earth material.

11.' An arc lamp electrode containing me 5 earth metal fluonds andbarium sulfate.

12. An arc lamp electrode conta' carbon, calcium fluond, rare-earthmetaluorid and barium sulfate, v 13. An arc lamp electrode containing rare-:0 earth metal sulfates and barium fluorid.

In testimony whereof, I hereunto aflix' my WMBOY

